As a method for measuring transmission/reception characteristics of a wireless terminal using an actual radio wave, a method for disposing a wireless terminal that is a measurement target and a measurement antenna in a radio wave anechoic chamber or a radio wave anechoic box and performing transmission and reception of radio waves between the wireless terminal and the measurement antenna while relatively changing a posture of the wireless terminal with respect to the measurement antenna to obtain measurement values necessary for evaluation in all directions, that is, a so-called over the air (OTA) environment test has been used in the related art.
In the measurement under the OTA environment, a method for rotating a wireless terminal disposed on an intersection point between a first axis (for example, a Z axis) and a second axis (for example, an X axis) orthogonal to the first axis around the first axis and revolving a measurement antenna in a plane (X-Z plane) including the first axis and the second axis or a plane (Y-Z plane) including the first axis and a third axis (Y axis) around the wireless terminal with a predetermined radius, and a method for disposing a wireless terminal at an intersection position between the first axis and the second axis, fixing a measurement antenna at a position on the second axis that is spaced away from the intersection position by a predetermined distance, and rotating the wireless terminal in a plane (X-Y plane) orthogonal to the first axis and in a plane including the first axis around the intersection point between the first axis and the second axis have been used. However, since the former method has a disadvantage in that a movable range of the measurement antenna becomes wide and a measurement system becomes large in size, generally, the latter method has been widely used.
In order to realize the latter method, a terminal holding rotation mechanism for rotating a wireless terminal held at an intersection position between two orthogonal axes (Z axis and X axis) around the intersection position to change a posture of the wireless terminal with respect to the measurement antenna, in a radio wave anechoic chamber or a radio wave anechoic box, is necessary.
The terminal holding rotation mechanism needs to have a terminal holding section that holds the wireless terminal and a rotation mechanism that rotates the terminal holding section around a vertical axis and a horizontal axis, as a basic structure.
As a specific configuration example, there is a general structure in which a vertical rotation mechanism that rotates a table around a vertical axis (Z axis) using a drive device such as a motor and a horizontal rotation mechanism disposed on the table are provided.
Further, in consideration of materials of component members, it is necessary that the terminal holding section and the rotation mechanism are configured to reduce an influence on radio waves transmitted and received between the wireless terminal and the measurement antenna as much as possible. Further, it is necessary that a metallic material of the motor that is a drive source of the rotation mechanism, or the like is coated with a radio wave absorbent at a position that is sufficiently spaced away from the terminal holding section.
Further, in the terminal holding section considered to have the greatest influence on the measurement and its peripheral section, it is necessary to use a material with a low specific dielectric constant that easily transmits and does not easily reflects radio waves, for example, a material formed of foam, synthetic resin, rubber, or the like.
In this way, a configuration example of the terminal holding rotation mechanism necessary for performing measurement of the wireless terminal is disclosed in Patent Document 1, for example.
The technique disclosed in Patent document 1 has, in consideration of measurement of a terminal that uses a 800 MHz band or a 2 GHz band, a structure in which opposite ends of a terminal holding section (arm) that directly supports a wireless terminal are supported to be rotatable around a horizontal axis through pulleys on upper ends of two poles standing up on a turntable that rotates around a vertical axis and the turntable and the terminal holding section are driven to rotate to change a posture of the wireless terminal, and reduces an influence on measurement, of the wireless terminal that uses the 800 MHz band or the 2 GHz band, by regulating lengths of the poles and a specific dielectric constant, or a pulley interval and the specific dielectric constant, for example.